1. Field of the Invention
The present invention is generally directed to measuring small relative angular orientation differences between two surfaces; such as roll bodies or other equipment surfaces.
2. Discussion of the Prior Art
A. Roll Parallel Measurement
The most common small angle parallel measuring method involves using surveyor instruments to measure the position of a roll against a nearby offset reference line. A survey transit, for example, is adjusted to be parallel to a reference line and the reference line is perpendicular to the roll to be measured. The transit is then rotated exactly 90 degrees giving a line of sight that is approximately parallel to the roll. A ruler is placed on each end of the roll and the transit line of sight is used to read the crosshair position at each ruler position. The difference in readings indicates if the roll is perpendicular to the offset reference line. The measurement of roll to roll parallel is performed by measuring each roll separately against the same offset reference line. The survey transit may need to be relocated for each roll to be measured. Optical tooling may be used instead of survey instruments for higher accuracy.
The accuracy of this method has been improved by using lasers and electronic measurements of the laser position instead of a visual line of sight and rulers. However, the improved equipment is relatively expensive and requires specialized training. It can also be time consuming to obtain the desired measurement when the roll is in an awkward position or hidden behind obstructions requiring the need for specialized equipment setups and fixtures.
In U.S. Pat. No. 3,947,970 Lesure describes a roll alignment gauge that is useful for roll alignment when one roll is directly above another roll. The device is essentially a vertical level that is adapted to measuring roll to roll twist with a micrometer. In U.S. Pat. No. 5,579,585 Schaeffer describes a device that projects a vertical and horizontal axis of a roll surface to determine alignment to an offset line, but surveyor methods and equipment are still required to actually measure the roll orientation.
B. Other Surfaces—Parallel Measurement
The use of survey methods, previously mentioned, is also applicable to a range of equipment surfaces and various kinds of machinery. The measuring methods for checking machinery surfaces for parallel orientation are essentially the same. The use of laser beams and electronic laser beam detectors are particularly suited to measuring the relative alignment of various surfaces and edges to a very high accuracy.
The use of inside micrometers to measure the parallel alignment between two surfaces is also a common way to measure small differences parallel orientation. This is useful when the measuring surfaces are readily available, correctly oriented to each other, closely spaced, and there is no obstructing equipment. However, in actual practice, the measuring surfaces may not be conveniently disposed to each other to facilitate such measurement. The surfaces to be checked may not be two parallel planes correctly oriented to each other, which is troublesome to measure accurately with standard measuring equipment. The surfaces may be a significant distance apart, beyond the measuring range of commonly available instruments. The surfaces may be rounded, making it particularly difficult to measure parallel orientation.